Selective deposition of amorphous silicon films on metal gates

ABSTRACT

A microelectronic device includes a metal gate with a metal gate upper surface. The metal gate is disposed in an interlayer dielectric first layer. The interlayer dielectric first layer also has an upper surface that is coplanar with the metal gate upper surface. A dielectric etch stop layer is disposed on the metal gate upper surface but not on the interlayer dielectric first layer upper surface.

TECHNICAL FIELD

Disclosed embodiments relate to semiconductive devices and processes ofmaking them.

BACKGROUND

The sizes of the microelectronic devices and other active and passiveelectrical components continuously scale down in attempts to increasedevice integrated-circuit density. Electrical contacts are fabricated toprovide an electrical access to the microelectronic devices built on awafer. Typically, lithography techniques are used to define the locationof contact vias to the devices. As the size of the microelectronicdevices and spacing between are scaled down, process challenges mayincrease.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the manner in which embodiments are obtained, amore particular description of various embodiments briefly describedabove will be rendered by reference to the appended drawings. Thesedrawings depict embodiments that are not necessarily drawn to scale andare not to be considered to be limiting in scope. Some embodiments willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 is a computer rendering from a photomicrograph of an array ofselectively deposited amorphous silicon upon a semiconductive bodyduring processing according to an example embodiment;

FIG. 2 is a cross-section elevation of a microelectronic device with aselectively deposited and converted amorphous silicon etch stop layerabove a metal gate according to an embodiment;

FIG. 2 a is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 during processing according to an embodiment;

FIG. 2 b is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 a after further processing according to anembodiment;

FIG. 2 c is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 b after further processing according to anembodiment;

FIG. 2 d is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 c after further processing according to anembodiment;

FIG. 2 e is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 d after further processing according to anembodiment;

FIG. 2 f is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 e after further processing according to anembodiment;

FIG. 2 g is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 f after further processing according to anembodiment;

FIG. 2 h is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 g after further processing according to anembodiment;

FIG. 3 is a cross-section elevation of a microelectronic device with aselectively deposited and converted amorphous silicon etch stop layerabove a metal gate according to an embodiment;

FIG. 4 is a process flow diagram according to an embodiment; and

FIG. 5 is a schematic of an electronic system according to anembodiment.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like structures maybe provided with like suffix reference designations. In order to showthe structures of various embodiments most clearly, the drawingsincluded herein are diagrammatic representations of integrated circuitstructures. Thus, the actual appearance of the fabricated structures,for example in a photomicrograph, may appear different while stillincorporating the claimed structures of the illustrated embodiments.Moreover, the drawings may show only the structures necessary tounderstand the illustrated embodiments. Additional structures known inthe art may have not been included to maintain the clarity of thedrawings.

Reference throughout this disclosure to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. The appearance ofthe phrases “in one embodiment” or “in an embodiment” in various placesthroughout this disclosure are not necessarily all referring to the sameembodiment. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

FIG. 1 is a computer rendering from a photomicrograph 100 of an array ofselectively deposited amorphous silicon upon a semiconductive substrateduring processing according to an example embodiment. A semiconductivebody 110 is illustrated. Upon the semiconductive body 110 is depositedan array of amorphous silicon that has been selectively deposited uponexposed upper surfaces of metal gates. A given selectively depositedbody of amorphous silicon 132 is depicted to illustrate a metal gatelength 128 and a metal gate width 130. The selectively deposited body ofamorphous silicon 132 shows definition between itself and otheroccurrences of selectively deposited bodies of amorphous silicon.

FIG. 2 is a cross-section elevation of a microelectronic device 200 witha selectively deposited and converted amorphous silicon etch stop layer233 above a metal gate according to an embodiment. As depicted, themicroelectronic device 200 illustrates a transistor. The transistorincludes a semiconductive body 210 with a gate dielectric 212 disposedupon an upper surface thereof. A gate electrode 214 is disposed on thegate dielectric 212. In an embodiment, the semiconductive body 210 mayinclude any semiconductor material to make a variety of integratedcircuits including passive, and active devices. In an embodiment, thesemiconductive body 210 includes a monocrystalline silicon structure. Inan embodiment, the semiconductive body 210 includes asilicon-on-insulator (SOI) structure. In an embodiment, thesemiconductive body 210 is a fin-shaped prominence that extends in theZ-direction away from a larger substrate of semiconductive material.Other embodiments for semiconductive material for the semiconductivebody 210 may use combined semiconductors, for example, indium phosphide,gallium arsenide, gallium nitride, silicon germanium, and siliconcarbide.

In an embodiment, the semiconductive body 210 comprises any material,e.g., SOI, gallium arsenide (GaAs), germanium (Ge), or SiGe. In anembodiment, the transistor is coupled to one or more metallizationlayers of integrated circuits having active and passive devices, such astransistors, switches, optoelectronic devices, capacitors, resistors,and interconnects. The one or more metallization layers of integratedcircuits are separated from adjacent metallization layers by dielectricmaterial such as interlayer dielectric layers (ILD).

In an embodiment, the transistor is isolated by structures such as ashallow trench isolation (STI) 216.

In an embodiment, the gate dielectric 212 includes silicon dioxide(SiO₂). In an embodiment, the gate dielectric includes siliconoxynitride (SiO_(x)N_(y)). In an embodiment, the gate dielectric 212includes silicon nitride (Si₃N₄). In an embodiment, the gate dielectric212 includes any two of the above given gate dielectrics.

In an embodiment, the gate dielectric 212 includes an oxide of a metalthat has a dielectric constant k higher than the dielectric constant ofSiO₂. Examples for such oxides may include zirconium oxide (ZrO₂),hafnium oxide (HFO₂), and lanthanum oxide (La₂O₄). The gate dielectric212 may be formed using any conventional technique that is known to oneof ordinary skill in the art of microelectronic device manufacturing,for example, using any suitable spinning-on, chemical vapor deposition(CVD), or physical vapor deposition (PVD, also known as sputtering)technique.

The gate electrode 214 is formed on the gate dielectric 212 and may be ametal gate such as copper (Cu). In an embodiment, the gate electrode 214is ruthenium (Ru). In an embodiment, the gate electrode 214 is nickel(Ni). In an embodiment, the gate electrode 214 is cobalt (Co). In anembodiment, the gate electrode 214 is chromium (Cr). In an embodiment,the gate electrode 214 is iron (Fe). In an embodiment, the gateelectrode 214 is manganese (Mn). In an embodiment, the gate electrode214 is titanium (Ti). In an embodiment, the gate electrode 214 isaluminum (Al). In an embodiment, the gate electrode 214 is hafnium (Hf).In an embodiment, the gate electrode 214 is tantalum (Ta). In anembodiment, the gate electrode 214 is tungsten (W). In an embodiment,the gate electrode 214 is vanadium (V). In an embodiment, the gateelectrode 214 is molybdenum (Mo). In an embodiment, the gate electrode214 is palladium (Pd). In an embodiment, the gate electrode 214 is gold(Au). In an embodiment, the gate electrode 214 is silver (Ag). In anembodiment, the gate electrode 214 is platinum (Pt). In an embodiment,the gate electrode 214 is any combination of the given metals.

FIG. 2 also illustrates the transistor with a source region 218 thatincludes a shallow source extension region (tip) 220 embodiment and adrain region 222 that includes a shallow drain tip 224 embodiment thatare formed at the opposite sides of the gate electrode 214. In anembodiment, the width 230 of the channel zone under the gate dielectric212 between the tip 220 embodiment and the tip 224 embodiment is in therange of 9 nanometers (nm) to 120 nm. This width 230 may be mapped tothe gate width 130 depicted in the computer rendering from thephotomicrograph 100 depicted in FIG. 1.

In an embodiment, the source region 218 and the drain region 222 may beformed using one of techniques known to one of ordinary skill in the artof microelectronic device manufacturing. In an embodiment, dopants arefirst implanted into the semiconductive body 210 at the opposite sidesof the gate electrode 214 to form the respective tips 220 and 224. As aresult the gate electrode 214 serves as a hard mask to preventimplantation of dopants into the portions of the semiconductive body 210below the gate dielectric 212 that defines the channel zone of thetransistor. In an embodiment, to form an n-MOS transistor, the dopantsare n-type dopants, for example, arsenic ions or phosphorus ions withthe concentration in the range of 10¹⁸ cm⁻³ to 10²¹ cm⁻³. In anembodiment, to form a p-MOS transistor structure, the dopants are p-typedopants, for example, boron ions having the concentration in the rangeof 10¹⁸ cm⁻³ to 10^(<)cm⁻³.

A nitride etch-stop layer (NESL) 235 is disposed across the uppersurface of the semiconductive body 210. It may now be understood thatthe NESL 235 may be substituted with another dielectric material thatmay act as an etch-stop layer. Spacers 236 are formed on thesemiconductive body 210 adjacent to sidewalls of the gate electrode 214.In an embodiment, the spacers 236 cover sidewalls of the gate electrode214 and part of the upper surface of the semiconductive body 210 atopposite sides of the gate electrode 214.

In an embodiment, the spacers 236 are an oxide material. In anembodiment, the spacers 236 are a nitride material. In an embodiment,the spacers 236 are a combination such as an oxynitride material. In anembodiment, the spacers 236 include silicon nitride. In an embodiment,the spacers 236 include silicon carbide. In an embodiment, the spacers236 include silicon boron nitride. In an embodiment any two of the abovesilicon-based materials may be combined to form the spacers 236. In anembodiment all three of the above silicon-based materials may becombined to form the spacers 236.

Formation of the spacers 236 can be done by conventional techniques thatare known to one of ordinary skill in the art of microelectronic devicemanufacturing. The spacers 236 may be used to protect the gate electrode214 from shorting to source and/or drain metal contacts duringprocessing. In an embodiment, the spacers 236 and the gate electrode 214serve as a mask to prevent implantation of the dopants into the regionsof the semiconductive body 210 below the spacers 236 and below the gateelectrode 214.

The gate electrode 214 is depicted disposed within an interlayerdielectric (ILD) first layer 239, and an ILD cap layer 243 is disposedabove the ILD first layer 239. A source contact 252 and a drain contact254 make contact with the upper surface of the semiconductive body 210by penetrating the ILD first layer 239, the ILD cap layer 243, and theNESL 235.

A gate contact 256 is disposed in the ILD cap layer 243 and itpenetrates the ILD cap layer 243 and the converted amorphous siliconlayer 233.

FIG. 2 a is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 during processing according to an embodiment. Themicroelectronic device 201 has been processed to a level that the gateelectrode 214, the spacers 236, and the ILD first layer 238 have beenpolished to form an upper surface 240. Processing after this mannerleaves exposed metal of the gate electrode 214 in comparison to exposeddielectrics of the spacers 236 and the ILD first layer 238.Consequently, the upper surface 240 is a substantially coplanar uppersurface of the ILD first layer 238 and the upper surface of the gateelectrode 214. The ILD first layer 238 depicted in FIG. 2 a is the ILDfirst layer 239 depicted in FIG. 2 before a penetrating etch. The NESL234 depicted in FIG. 2 a is the NESL 235 depicted in FIG. 2 before apenetrating etch.

FIG. 2 b is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 b after further processing according to anembodiment. The microelectronic device 202 has been blanket depositedwith an amorphous silicon layer 231. Interaction between the amorphoussilicon layer 231 and the metal of the gate electrode 214, however, hascreated an amorphous silicon 232 within the amorphous silicon layer 231.One may refer to this process result as “partially selectivedeposition”.

In an embodiment, an amorphous silicon 232 is formed by chemical vapordeposition (CVD) of a silicon precursor to achieve the partiallyselective deposition, followed by an etch-back process to isolate theamorphous silicon 232 and remove the original amorphous silicon layer231. In an embodiment, a silicon-containing chemical compound, such asbut not limited to silane (SiH₄) is used to deposit the amorphoussilicon. In an embodiment, disilane (Si₂H₆) can be used to deposit theamorphous silicon. In an example embodiment, the substrate is exposed tothe Si containing precursor, for example silane (SiH₄), at a temperatureof 200-800 degrees Celsius, and at a pressure of 0.1-10 Torr.

In an embodiment, a plasma-enhanced CVD (PECVD) process is used toachieve the partially selective deposition, followed by an etch-backprocess to isolate the amorphous silicon 232 from the original amorphoussilicon layer 231. In an embodiment, a partially selective PECVD processwas used to achieve an approximate 600 Angstrom (Å) thick amorphoussilicon layer 231. After an etch-back process the structure depicted inFIG. 1 was achieved and photographed. In an embodiment of the presentinvention, a precursor that contains a silicon-containing chemicalcompound, such as but not limited to silane (SiH₄) or disilane (Si₂H₆)can be used for PECVD a-Si growth. In an example embodiment, thesemiconductive body 210 is exposed to the Si containing precursor, forexample silane (SiH₄), at a temperature of 250-400 degrees Celsius, at apressure of 1-10 Torr and for a time duration of 1-30 seconds with radiofrequency (RF) power of 10-3000 Watts. In an embodiment, an inert gassuch as but not limited to hydrogen (H₂) can be used in addition tosilane (SiH₄) or disilane (Si₂H₆). For example, a mixture of silane andhydrogen (SiH₄+H₂) or a mixture of disilane and hydrogen (Si₂H₆+H₂) canbe used as reactants. Next, the entire substrate is exposed to thesecond precursor to remove the plurality of amorphous semiconductor fromthe dielectric surfaces (spacer and ILD). In one embodiment, the secondprecursor is an etchant gas, such as but not limited to hydrogen (H₂) orhelium (He). In one embodiment, the first precursor is removed from thesemiconductive body 210 before exposing the second precursor to thesemiconductive body 210, so that only the second precursor reacts withthe plurality of amorphous semiconductor deposits. In the case where thefirst precursor comprises silane (SiH₄) only, the flow of the firstprecursor to the semiconductive body 210 is stopped before allowing thesecond precursor, for example hydrogen (H₂), to flow to thesemiconductive body 210. On the other hand, if the first precursorcomprises a mixture of silane and hydrogen (SiH₄+H₂), then the flow ofsilane (SiH₄) to the semiconductive body 210 is stopped while thehydrogen (now acting as the second precursor) continues to flow to thesemiconductive body 210. In a specific embodiment, the semiconductivebody 210 is exposed to the second precursor, for example hydrogen (H₂),at a temperature of 200-450 degrees Celsius, at a pressure of 0.1-10Torr and at a time duration of 5-300 seconds.

The second precursor is able to easily remove the plurality of amorphoussemiconductor deposits from the adjoining dielectric layers and spacersdue to the weak chemical bonding between the nuclei of each amorphoussemiconductor deposit and the dielectric layers and spacers. Inparticular, the second precursor reacts with the plurality of amorphoussemiconductor deposits and converts the plurality of amorphoussemiconductor deposits into a gas phase, thus removing the plurality ofamorphous semiconductor deposits from the dielectric layers and spacers.On the other hand, the nuclei of amorphous semiconductor layers have astrong chemical bond with the metal gate regions. Due to the strongchemical bonds, the second precursor only removes a portion of theamorphous semiconductor layers that were deposited on the gate region(differential etch rate between the amorphous silicon deposited on thegate as opposed to the surrounding dielectric regions). The thickness ofthe amorphous semiconductor layers deposited during the amorphoussilicon deposition step and the duration of exposing the secondprecursor to the semiconductive body 210 can be controlled so as toeffectively remove the plurality of amorphous semiconductor deposits andyet maintain sufficient thickness for the amorphous semiconductor layeron the gate regions.

In an embodiment, the metal lattice of the gate electrode 214 causes theamorphous silicon 232 to have a different atomic or molecular packingsuch that during an etch process, the etch recipe is selective toremoving the amorphous silicon layer 231 and leaving behind theamorphous silicon 232. Other mechanisms may better explain the partiallyselective deposition phenomenon, followed by the etch back result.

FIG. 2 c is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 b after further processing according to anembodiment.

The microelectronic device 202 depicted in FIG. 2 b has been processedto achieve the microelectronic device 203 depicted in FIG. 2 c. In anembodiment, a blanket etch has been carried out on the microelectronicdevice 202 depicted in FIG. 2 b, and the etch has been selective toleaving behind the amorphous silicon 232 that was in contact with themetal of the gate electrode 214.

In an embodiment, FIG. 2 c is a cross-section elevation of themicroelectronic device depicted in FIG. 2 a, where a deposition of theamorphous silicon 232 has been achieved only upon the metal of the gateelectrode 214. One may refer to this process result as “selectivedeposition”. In this embodiment, a selective deposition of the amorphoussilicon 232 has used the metal of the gate electrode 214 as a catalystto cause deposition of the amorphous silicon 232 onto the metal beforeany deposition thereof, if at all, onto the dielectric of the spacer 236and the first ILD 238. Other mechanisms may better explain the selectivedeposition phenomena.

In an embodiment, a CVD process is used with a silicon precursor toachieve the selective deposition of the amorphous silicon 232 onto thegate electrode 214 but not onto the upper surface of the ILD first layer238. A silicon-containing chemical compound, such as but not limited tosilane (SiH4) or disilane (Si2H6) can be used to deposit the amorphoussilicon. In an embodiment, the substrate is exposed to the Si containingprecursor, for example silane (SiH4), at a temperature of 200-800degrees Celsius, at a pressure of 0.1-10 Torr. In an embodiment, a PECVDprocess is used with a silicon precursor to achieve the selectivedeposition of the amorphous silicon 232 onto the gate electrode 214 butnot onto the upper surface of the ILD first layer 238. In an embodimentof the present invention, a precursor that contains a silicon-containingchemical compound, such as but not limited to silane (SiH4) or disilane(Si2H6) can be used for PECVD a-Si growth. In a specific embodiment, thesemiconductive body 210 is exposed to the Si containing precursor, forexample silane (SiH4), at a temperature of 250-400 degrees Celsius, at apressure of_(—)1-10 Torr and for a time duration of 1-30 seconds with RFpower of 10-3000 Watts. In all of these deposition embodiments, it isunderstood that the disclosed processes are carried out under conditionsto make the amorphous silicon 232 more likely to remain on the gateelectrode 214 than for any amorphous silicon layer to remain on the ILDfirst layer 238 or the spacers 236. Further in all of the depositionembodiments, one may refer to the process as getting the amorphoussilicon to accumulate on the metal gate 214 upper surface and not on theILD first layer 238 upper surface. The accumulation may be achieved withor without an etch back process as described.

FIG. 2 d is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 c after further processing according to anembodiment. The microelectronic device 204 has been processed to convertthe amorphous silicon 232 into a more etch-stop capable material. In anembodiment, however, the amorphous silicon 232 may be a sufficient etchstop material that no conversion is needed, depending upon the specificapplication.

In an embodiment, the amorphous silicon 232 is converted into adielectric material and is referred to as a converted amorphous siliconetch stop layer 233. Conversion of the amorphous silicon 232 is carriedout by a plasma nitridation in the presence of ammonia to cause theconverted amorphous silicon etch stop layer 233 to be a silicon nitridematerial according to an embodiment. Conversion of the amorphous silicon232 is carried out by a plasma oxidation in the presence of oxygen tocause the converted amorphous silicon etch stop layer 233 to be asilicon oxide material according to an embodiment. In an embodiment,conversion of the amorphous silicon 232 is carried out by a plasmacarbonization in the presence of methane to cause the convertedamorphous silicon etch stop layer 233 to be a silicon carbide material.In an embodiment, plasma conversion of the amorphous silicon 232 iscarried out by a plasma process that uses any two or all three of thenitride, oxide, or carbide materials or the like to achieve theconverted amorphous silicon etch stop layer 233.

In an embodiment, the amorphous silicon 232 is partially selectivelydeposited or selectively deposited and it is used as a placeholder. Theamorphous silicon 232 is capped with a dielectric layer (not pictured)and an etch back is done to expose the amorphous silicon 232 through thedielectric layer. Thereafter, the amorphous silicon 232 is wet-etchremoved and a replacement dielectric 233 is filled into the recessesleft by the wet etch.

Further processing is depicted herein and in correspondence with FIGS. 2e, 2 f, 2 g, and 2 h.

FIG. 2 e is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 d after further processing according to anembodiment. The microelectronic device 205 has been blanket depositedwith an ILD cap layer 242 which has an ILD cap layer upper surface 250.Consequently, the upper surface 240 has been obscured on the ILD firstlayer 238. The ILD cap layer 242 depicted in FIG. 2 e is the ILD caplayer 243 depicted in FIG. 2 before a penetrating etch.

FIG. 2 f is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 e after further processing according to anembodiment. The microelectronic device 206 has been processed with adirectional etch through a mask (not pictured) to form recesses in theseveral layers. A source contact via 244 has penetrated the ILD caplayer 242 to make it a penetrated ILD cap layer 243, the ILD first layer238 to make it a penetrated ILD first layer 239, and the NESL 234 tomake it a penetrated NESL 235. The directional etch has also formed adrain contact via 246 with similar results. The directional etch hasalso formed a gate electrode contact partial via 248 that has stopped onthe converted amorphous silicon etch stop layer 233 according to anembodiment.

In an embodiment, the directional etch is prepared such that etchingstops both on the semiconductive body 210 through the penetrated ILD caplayer 243, the penetrated ILD first layer 239, and the penetrated NESL235, and the directional etch stops on the gate electrode 214 as well bypenetrating the converted amorphous silicon etch stop layer 233. Thiswill be described further.

FIG. 2 g is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 f after further processing according to anembodiment. The microelectronic device 207 has been processed to fillsource- and drain contacts 252 and 254, respectively into the respectivesource contact via 244 and drain contact via 246. By leaving the gateelectrode contact partial via 248 unfilled, the process may requiremasking thereof.

FIG. 2 h is a cross-section elevation of the microelectronic devicedepicted in FIG. 2 g after further processing according to anembodiment. The microelectronic device 208 has been processed with asecond directional etch that is self-aligning to the gate electrodecontact partial via 248 depicted in FIG. 2 g. As a consequence, the gateelectrode contact via 249 has been formed that has stopped on the gateelectrode 214.

As discussed previously, a single directional etch may simultaneouslyform the gate electrode contact via 249 to stop on the gate electrode214 as well as the respective source contact via 244 and drain contactvia 246 that stop on the semiconductive body 210. The single directionetch may be prepared by adjusting both the etch resistivities and thethicknesses of the NESL 234 and the converted amorphous silicon etchstop layer 233 such that after the respective source- and drain contactvias 244 and 246 have reached the NESL 234, etching through the ILD caplayer 238 and the converted amorphous silicon etch stop layer 233 arecompleted at about the same time the NESL 234 has been breached.

As discussed previously, two back-to-back directional etches may formthe gate electrode contact via 249 to stop on the gate electrode 214 aswell as the respective source contact via 244 and drain contact via 246that stop on the semiconductive body 210. The back-to-back directionaletches may be done by first etching and stopping on the semiconductivebody 210 in the respective source contact via 244 and drain contact via246, followed by second etching that forms the gate electrode contactvia 249 to stop on the gate electrode 214. This second etching isselective to leaving the semiconductive material of the semiconductivebody 210. In an embodiment, back-to-back etches may be done in thereverse order, i.e., the gate electrode contact via 249 is first formedin a first etch, and the respective source contact via 244 and draincontact via 246 are formed in a second etch that is selective to leavingthe metal of the gate electrode 214.

Reference is again made to FIG. 2. The microelectronic device 200 hasbeen thus far fabricated by a partially selective deposition- or aselective deposition and conversion of an amorphous silicon etch stoplayer 233.

FIG. 3 is a cross-section elevation of a microelectronic device 300 witha selectively deposited and converted amorphous silicon etch stop layer333 above a metal gate 314 according to an embodiment. As depicted, themicroelectronic device 300 illustrates a transistor. The transistorincludes a semiconductive body 310 with a gate dielectric 312 disposedupon an upper surface thereof. A gate electrode 314 is disposed on thegate dielectric 312. In an embodiment, the semiconductive body 310includes an SOI structure. In an embodiment, the semiconductive body 310is a fin-shaped prominence that extends from a larger substrate ofsemiconductive material. Other embodiments for semiconductive materialfor the semiconductive body 310 may use combined semiconductors, forexample, indium phosphide, gallium arsenide, gallium nitride, silicongermanium, and silicon carbide.

In an embodiment, the semiconductive body 310 comprises any material,e.g., SOI, gallium arsenide (GaAs), germanium (Ge), SiGe, and the like.In an embodiment, the semiconductive body 310 includes one or moremetallization layers of integrated circuits having active and passivedevices, such as transistors, switches, optoelectronic devices,capacitors, resistors, and interconnects. The one or more metallizationlayers of integrated circuits are separated from adjacent metallizationlayers by dielectric material such as ILD layers.

In an embodiment, the transistor is isolated by structures such as anSTI 316. The gate electrode 314 is formed on the gate dielectric 312 andmay be a metal gate that is any combination of the given metals.

FIG. 3 also illustrates the transistor with a source region 318 thatincludes a shallow source extension region tip 320 embodiment and adrain region 322 that includes a shallow drain tip 224 embodiment thatare formed at the opposite sides of the gate electrode 314. In anembodiment, the width 330 of the channel zone under the gate dielectric312 between the tip 320 embodiment and the tip 324 embodiment is in therange of 9 nm to 120 nm. This width 330 may be mapped to the gate width130 depicted in the computer rendition of the photomicrograph 100depicted in FIG. 1.

In an embodiment, the source region 318 and the drain region 322 may beformed using one of techniques known to one of ordinary skill in the artof microelectronic device manufacturing. In an embodiment, dopants arefirst implanted into the substrate 310 at the opposite sides of the gateelectrode 314 to form the respective tips 320 and 324. As a result thegate electrode 314 serves as a hard mask to prevent implantation ofdopants into the portions of the semiconductive body 310 below the gatedielectric 312 that defines the channel zone of the transistor. In anembodiment, to form an n-MOS transistor, the dopants are n-type dopants,for example, arsenic ions or phosphorus ions with the concentration inthe range of 10¹⁸ cm⁻³ to 10²¹ cm⁻³. In an embodiment, to form a p-MOStransistor structure, the dopants are p-type dopants, for example, boronions having the concentration in the range of 10¹⁸ cm⁻³ to 10²¹ cm⁻³.

An NESL 335 is disposed across the upper surface of the semiconductivebody 310. Inner spacers 337 and outer spacers 336 are formed on thesemiconductive body 310. The inner spacers 337 are adjacent to sidewallsof the gate electrode 314 and the outer spacers 336 are adjacent to theinner spacers 337. In an embodiment, the inner spacers 337 coversidewalls of the gate electrode 314 and part of the upper surface of thesemiconductive body 310 at opposite sides of the gate electrode 314.

In an embodiment, the inner spacers 337 are a different material fromthe outer spacers 336.

The gate electrode 314 is depicted disposed within an ILD first layer339, and an ILD cap layer 343 is disposed above the ILD first layer 339.A source contact 352 and a drain contact 354 make contact with the uppersurface of the semiconductive body 310 by penetrating the ILD firstlayer 339, the ILD cap layer 343, and the NESL 335.

A gate contact 356 is disposed in the ILD cap layer 343 and itpenetrates the converted amorphous silicon layer 333.

FIG. 4 is a process flow diagram 400 according to an embodiment.

At 410, the process includes forming an amorphous silicon etch stoplayer by a selective deposition upon a metal gate electrode that isdisposed in an ILD first layer. In a non-limiting example embodiment,this process includes forming a selective deposition or it may include apartially selective deposition.

At 412, the process includes etching the amorphous silicon etch stoplayer to remove any amorphous silicon that is not in contact with metalgate electrode material. In a non-limiting example embodiment, thisprocess includes forming a partially selective deposition, followed bythe etching.

At 420, the process includes forming source- and drain contact viasthrough the ILD first layer and through an ILD cap layer.

At 422, the process includes forming a gate electrode contact partialvia while forming the source- and drain contact vias.

At 424, the process includes forming a gate electrode contact completevia simultaneously with forming the source- and drain contact vias.

FIG. 5 is a schematic of an electronic system 500 according to anembodiment. The electronic system 500 as depicted can embody a die witha transistor that includes a selectively deposited etch stop layer abovea metal gate electrode as set forth in this disclosure. In anembodiment, the electronic system 500 is a computer system that includesa system bus 520 to electrically couple the various components of theelectronic system 500. The system bus 520 is a single bus or anycombination of busses according to various embodiments. The electronicsystem 500 includes a voltage source 530 that provides power to theintegrated circuit 510. In some embodiments, the voltage source 530supplies current to the integrated circuit 510 through the system bus520.

The integrated circuit 510 is electrically coupled to the system bus 520and includes any circuit, or combination of circuits according to anembodiment. In an embodiment, the integrated circuit 510 includes aprocessor 512 that can be of any type. As used herein, the processor 512may mean any type of circuit such as, but not limited to, amicroprocessor, a microcontroller, a graphics processor, a digitalsignal processor, or another processor. Other types of circuits that canbe included in the integrated circuit 510 are a custom circuit or anapplication-specific integrated circuit (ASIC), such as a communicationscircuit 514 for use in wireless devices such as cellular telephones,pagers, portable computers, two-way radios, and similar electronicsystems. In an embodiment, the processor 510 includes on-die memory 516such as static random-access memory (SRAM). In an embodiment, theprocessor 510 includes on-die memory 516 such as embedded dynamicrandom-access memory (eDRAM).

In an embodiment, the electronic system 500 also includes an externalmemory 840 that in turn may include one or more memory elements suitableto the particular application, such as a main memory 542 in the form ofRAM, one or more hard drives 544, and/or one or more drives that handleremovable media 546, such as diskettes, compact disks (CDs), digitalvariable disks (DVDs), flash memory keys, and other removable mediaknown in the art.

In an embodiment, the electronic system 500 also includes a displaydevice 550, an audio output 560. In an embodiment, the electronic system500 includes a controller 570, such as a keyboard, mouse, trackball,game controller, microphone, voice-recognition device, or any otherdevice that inputs information into the electronic system 500.

As shown herein, the integrated circuit 510 can be implemented in anumber of different embodiments, including a transistor that includes aselectively deposited etch stop layer above a metal gate electrode, anelectronic system, a computer system, one or more methods of fabricatingan integrated circuit, and one or more methods of fabricating anelectronic assembly that includes a transistor that includes aselectively deposited etch stop layer above a metal gate electrode asset forth herein in the various embodiments and their art-recognizedequivalents. The elements, materials, geometries, dimensions, andsequence of operations can all be varied to suit particular packagingrequirements.

The Abstract is provided to comply with 37 C.F.R. §1.72(b) requiring anabstract that will allow the reader to quickly ascertain the nature andgist of the technical disclosure. It is submitted with the understandingthat it will not be used to interpret or limit the scope or meaning ofthe claims.

In the foregoing Detailed Description, various features are groupedtogether in a single embodiment for the purpose of streamlining thedisclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments of the inventionrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter lies in lessthan all features of a single disclosed embodiment. Thus the followingclaims are hereby incorporated into the Detailed Description, with eachclaim standing on its own as a separate preferred embodiment.

It will be readily understood to those skilled in the art that variousother changes in the details, material, and arrangements of the partsand method stages which have been described and illustrated in order toexplain the nature of this invention may be made without departing fromthe principles and scope of the invention as expressed in the subjoinedclaims.

1. A process comprising: forming an amorphous silicon film upon asubstrate, the substrate including: a gate electrode disposed above asemiconductive body, including a gate electrode upper surface and atlease one sidewall; a nitride etch stop layer (NESL) disposed above andon the semiconductive body; a spacer disposed on the at least onesidewall; and an interlayer dielectric (ILD) first layer including anILD first layer upper surface, wherein the gate electrode upper surfaceand the ILD first layer upper surface are substantially coplanar,wherein forming the amorphous silicon film is carried out underconditions to accumulate on the metal gate upper surface and not on theILD first layer upper surface; and forming an etch stop layer from theamorphous silicon film.
 2. The process of claim 1, wherein accumulationof the amorphous silicon film is achieved by selectively etching backthe amorphous silicon film to remove amorphous silicon disposed upon theILD first layer upper.
 3. The process of claim 1, further including:forming an ILD cap layer over the ILD first layer; etching source- anddrain contact vias through the ILD cap layer, the ILD first layer, andthe NESL; and etching a gate electrode partial via through the ILD caplayer that stops on the etch stop layer.
 4. The process of claim 1,further including: forming an ILD cap layer over the ILD first layer;etching source- and drain contact vias through the ILD cap layer, theILD first layer, and the NESL; and simultaneously etching a gateelectrode complete via through the ILD cap layer that stops on the gateelectrode.
 5. The process of claim 1, further including converting theamorphous silicon to a dielectric material under nitriding conditions toachieve silicon nitride.
 6. The process of claim 1, further includingconverting the amorphous silicon to a dielectric material underoxidizing conditions to achieve silicon oxide.
 7. The process of claim1, further including converting the amorphous silicon to a dielectricmaterial under carburizing conditions to achieve silicon carbide.
 8. Theprocess of claim 1, further including converting the amorphous siliconto a dielectric material under conditions to achieve silicon oxynitride.9. The process of claim 1, further including: forming an ILD cap layerover the ILD first layer; etching source- and drain contact vias throughthe ILD cap layer, the ILD first layer, and the NESL; followed byetching a gate electrode complete via through the ILD cap layer thatstops on the gate electrode.
 10. The process of claim 1, furtherincluding: forming an ILD cap layer over the ILD first layer; etching agate electrode complete via through the ILD cap layer that stops on thegate electrode; followed by etching source- and drain contact viasthrough the ILD cap layer, the ILD first layer, and the NESL.
 11. A gatetransistor comprising; a semiconductive body; a gate electrode disposedon a gate dielectric film disposed on the semiconductive body, whereinthe gate electrode includes a gate electrode upper surface; aninterlayer dielectric layer (ILD) first layer including an ILD firstlayer upper surface, wherein the gate electrode upper surface and theILD upper surface are substantially coplanar; an etch stop layerdisposed on the semiconductive body and below the ILD first layer; andan etch stop layer disposed on the metal gate upper surface but not onthe first ILD layer upper surface.
 12. The transistor of claim 11,wherein the gate electrode is metal.
 13. The transistor of claim 11,further including: an ILD cap layer disposed on the ILD first layer;source-and drain contacts disposed in respective source- and draincontact vias that penetrate the ILD cap layer, the ILD first layer, andthe etch stop layer disposed on the semiconductive body; and a gateelectrode contact disposed in a gate electrode contact via thatpenetrates the ILD cap layer and the etch stop layer disposed on themetal gate upper surface.
 14. The transistor of claim 11, furtherincluding spacers disposed on the semiconductive body adjacent tosidewalls of the gate electrode.
 15. The transistor of claim 11, furtherincluding spacers disposed on the semiconductive body, wherein thespacers include inner spacers and outer spacers, wherein the innerspacers are adjacent to sidewalls of the gate electrode and the outerspacers are adjacent to the inner spacers.
 16. The transistor of claim11, wherein the gate electrode is metal, the transistor furtherincluding: an ILD cap layer disposed on the ILD first layer; source-anddrain contacts disposed in respective source- and drain contact viasthat penetrate the ILD cap layer, the ILD first layer, and the etch stoplayer disposed on the semiconductive body; a gate electrode contactdisposed in a gate electrode contact via that penetrates the ILD caplayer and the etch stop layer disposed on the metal gate upper surface;and spacers disposed on the semiconductive body.
 17. The transistor ofclaim 11, wherein the gate electrode is metal, the transistor furtherincluding: an ILD cap layer disposed on the ILD first layer; source-anddrain contacts disposed in respective source- and drain contact viasthat penetrate the ILD cap layer, the ILD first layer, and the etch stoplayer disposed on the semiconductive body; a gate electrode contactdisposed in a gate electrode contact via that penetrates the ILD caplayer and the etch stop layer disposed on the metal gate upper surface;and spacers disposed on the semiconductive body, wherein the spacersinclude inner spacers and outer spacers, wherein the inner spacers areadjacent to sidewalls of the gate electrode and the outer spacers areadjacent to the inner spacers.
 18. A computing system comprising: asemiconductive body that is part of a microelectronic die; a gateelectrode disposed on a gate dielectric film disposed on thesemiconductive body, wherein the gate electrode includes a gateelectrode upper surface; an interlayer dielectric layer (ILD) firstlayer including an ILD first layer upper surface, wherein the gateelectrode upper surface and the ILD upper surface are substantiallycoplanar; an etch stop layer disposed on the semiconductive body andbelow the ILD first layer; and an etch stop layer disposed on the metalgate upper surface but not on the first ILD layer upper surface; andexternal memory coupled to the microelectronic die.
 19. The computingsystem of claim 18, wherein the computing system is part of one of acellular telephone, a pager, a portable computer, a desktop computer,and a two-way radio.